William a



UNITED STATES PATENT orrics.

WILLIAI A. CHAPIN, OF CHICAGO. ILLINOIS. ASSIGNOB TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS. A CORPOBATION OF ILLINOIS.

AUTOMATIC TELEPHONE. SYSTEM.

Specification of Letters Patent.

Patented May 31. 1921.

.Applicatlon filed October 28, 1916. Serial No. 128,226.

To all whom-it may concern; 1

Be it known that I, l\'ii.i.i.-\.\i A. (hurts, a citizen of. the United States ofAmenca,

and a resident of Chicago. county of Cook,

and State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following 'is a specification.

My invention relates in general to automatic telephone systems but is concerned more particularly with such systems as include a main exchange and one or more branch or private automatic exchanges auxiliary thereto. In systems of the foregoing character it is often desirable to give only'a limited number of the substations at a private automatic exchange access to, the main exchange, the remaining substations being restricted to local calling within the branch. This condition exists usually in the, case of a large commercial establishment served by an automatic private branch exchange connected with a main exchange by tri nk lines.

I In an installation of this kind it is generally required that the principal ofiicials and department heads should be able to call main exchange as well as local subscribers, while theminor employees are unable to call the main exchange subscribers but are restricted to local calls.-

The object of my invention. therefore, is to provide an improvement 'for automatic private branch exchange systcms'whereby the service at certain substations may be restricted while the serv c at other substations is unlimited; witlilvut, however: requiring difierent types of apparatus or separate groupinfl of the subscribers lines.

nilic groups of 100 lines each.

I Connector switches are provided. in each group for connecting with called lines, which connectors 'are accessible to calling lines through the medium of individual line switches arld selector switches in the usual manner. One

of the selector levels. usually the tenth, may

be reserved for the trunk lines extending to the main exchange and terminating therein in second selector switches. In case the exchange is of small capacity, having not more tha 90 lines. the selector switches may be omitte and a combined selector and connector is used (see Fig. 2) which operates as a connector on the first nine levels and as a selector on the tenth level. all of which will be explained more in detail hereafter.

All the apparatus shown is in general well known in the art and willbe described but briefly, reference. being had to prior patents hereinafter mentioned in lieu oi a detailed descri )tion.

Th substation A may be of any approved automatic type, such, for example, as the substation shown in British patent to Martin. No. 1419 of 1910. As represented here- To accomplish the forkgoing and other.

useful ends my invention comprises means which will be fully described hereinafter,

reference,being had to the accompanying drawing, in which Figure 1. illustrates the I invention by means of automatic private branchexchange equipment comprising a.

calling substation A, an individual line switch C, and a trunk line terminating in a selector switch E; while in Fig. 2, which may be'considered a modification of Fig. 1, the invention is shown applied to s/somewhat different type of switch. v

Referring to Fig. 1 of the drawing, the

automatic private branch exchange ofwhiclr the equipmentthnrein shown is a part, may have a capacity of 900 lines divided into in, it comprises essentially the receiver 2, transmitter 3, switch hook 4, ringer 5 and condenser 6. Being an automatic substation. there is also provided a pair of im' pulse springs 7 and 8 controlled by an im pulsewheel 9 through the medium of a. I

fingerhole dial (not shown).

The. line conductors 11 and. 12 of the substation A are connected at the rivate branch exchange to the individual ine switch C which is of the general type of line switch disclosed in the British .patent to James,

particular type shown 'in U. S. Letters Pat- No. 26.301 of 1906; being-however, of the ent No. 1,078,690, granted Jan. 17, 1912, to 7 Frank Newforth. Through the medium of line switchC the. line of substation A when calling is given access to a plurality of trunk lines extendin to selector switches.

The line switch C and a plurality of similar line switches are controlled in their trunk selecting operations by means of a master switch D. The master switch D is of the general typo'of master switch disclosed in the above mentioned British pateat to James, No. 26,301 of 1906; being. however, more nearly of the particular type disclosed in the-British patent to Martin, No. -1419 of 1910, also previously referred to.

As is well known, the function of the master switch is to maintain the plungers of all idle line switches which it controls in popition before the terminals of an idle trunk One of the trunk lines to which the line switch C has access is shown in Fig. 1 extendin%to the selector switch E. The selector lector switch disclosed in U. S. Letters Patent No. 815,321, granted March 31, 1906, to Keith, Erickson, and Erickson; the side switch and rivate magnet being omitted, however, and the circuits being modified in accordance with the two-wire system of control. The circuits are further modified by the addition in accordance with my invention, of a fourth conductor to the trunk line extending between the line switch and the selector switch, over'which, in certain instances which will be pointed out, a circuit is closed by which the selectorswitch is prevented from connecting with a trunk line to the main exchange.

While I have shown throughout the drawing a plurality of batteries, it is understood that there is preferably but one battery having its positive pole grounded, the various battery leads of the drawing being connected together and extended to the negative pole thereof. The reference character Q, indicates a busy signaling machine of the usual and well known type. 4

Having given a general description of the apparatus involved I will now proceed to explain more in detail the operation of the same. It will firstbe briefly explained how the connection is extended from the calling substation A to the selector switch E as zownin Fig. 1 of the drawing, after which the operation of the selector switch in selecting a trunk line to the main exchange will be described, it being assumed that the substation A has unlimited service. Thereafter it will be assumed that the substation A has restricted service, and the operation of the selector switch when an attempt is made to call the main exchange by the restricted service subscriber will be described.

\Vhen the calling subscriber at substation A removes his receiver to initiate the call, an energizing circuit is completed over the line conductors 11 and 12 for the line relay 14 of the line switch 0. Upon attracting its armature; the line relay 14 closes a circuit for the'pull-in winding 18. Upon energizing, the pull-in winding operates both the plunger-elm 15 and the cut-off armature 16; the former through the medium of its plunger (not shown) forcing the bank springs 30-33 inclusive, into engagement, respectively, with contacts 34--37, inclusive; and the latter disconnecting the line conductors 11 and 12, respectively, from ground and from the line relay 14. By the engagement may be of the general type ofse-v of bank springs 30 and 33 with contacts 34 and 37, respectively, the line conductors 12 and 11 are extended through normally closed contacts of the switching relay 63 to the double wound line relay 50 of the selector E.

The line relay 50 is accordingly energized over the loop circuit including substation A and, upon attracting its armature, closes a circuit for the slow acting release relay 51. Upon energizing, the release relay closes a holding circuit for the line switch C which may be traced from ground G by we of the working contact of armature 49 an the said armature, conductor 48, contact 35, bank spring 31, and the holding winding 17 to battery B. Since the line relay 14 is slow acting, it retains its armature to maintain the pull-in winding 18 energized until after the above holding circuit has been established. A branch of the holding circuit extends by way of conductor 20 to multiple test contacts in the banks of connector switches having access to the line'of substation A whereby a ground potential on these test contacts the said line is made busy. A second branch of the holding circuit extends by way of conductor 46 to the test contact in the master switch bank which is associated with the trunk line terminating in selector E, whereby the master switch D is operated in the usual manner to advance the plungers of all the remaining idle line switches of the group which it controls into position before the terminals of the next idle trunk line. The engagement of bank spring 32 with contact 36 is functionless at this time, for in the case where substation A has unlimited service the terminals 38 and 39 will not be connected.

The foregoing operations have occurred in response to the removal of the receiver at substation A. It has been assumed that the calling subscriber desires to connectwith a suhscril'ier in the mainexchange and he will therefore proceed to operate his calling device in accordance with the digit 0, for previously stated, the trunk lines extending to the main exchange terminate in the tenth level of the selector E. By the operation'of the calling device a series of ten interruptions is produced in the circuit of the line relay 50 of the selector E. At each interruption Jf its circuit, the line relay 50 deenergizes momentarily and sends an impulse from ground G through the slow acting relay 52 and the vertical magnet 53 in series. In response to these impulses the veitical magnet operates to raise the switch shaft step-bystep until wipers 70, 71 and 72 arrive at the tenth horizontal level of bank contacts. The '--w acting. relay 52 is energized in series th the vertical magnet and retains its armature attracted during the vertical movement of the switch. Upon the first upward movement of the shaft the oil-normal springs 58 are closed,

- has already been connected to have ground potential upon it, w

thereby completing aninitial energizing circuit for relay 55, which may be traced as follows: Ground at G, the working contacts of armature 49, armature of relay 52 and its working contact, junction point 80, the said oil-normal springs-5 8 and the winding of relay 55 to battery. Upon energizing, relay 55 looks itself at its lower armature independent of the relay 52 and at its upper armature prepares a circuit for the rotary magnet 54, which is ,held open ho ever during the vertical movement of the switch by the relay 52. At this point it should be mentioned that by the closure of the off-normal springs 58, the line switchin relay 63 was connected in series with re ay 55. The junction point 80, however, round as previously described. Hence it will be seen that line switching relay 63 is short circuitcd for the present and remains inoperative.

When the slow acting relay. 52 de e'ner- 'gizes at the end of the series of impulses it completes at'its back contact the previously mentioned circuit of the rotary magnet. Upon energizing, the rotary magnet operates to rotate the wipers 70, 71 and-72 into engagement with the first set of bankcontacts of the tenth horizontal 'level. Near the end of its stroke, the rotary magnet breaks at its armature 73 the locking circuit of relay 55; breaks at its armature74 the cir cuit connecting the switching relay 63 with the relay 55, a. branch of which circuit extends to the rivate wiper 71; and at its armature 75,,d1sconnects the conductor 47. In

the case under present consideration, however, this latter operation is of no conse-' quence. Upon de'einergizing, the relay 55 breaks the circuit of the rotary magnet, which accordingly retracts its armature to close its several contacts represented herein as being controlled by the separate armatnres 73, 74, and 75. The operation now depends upon whether the first trunk line, the terminals of which are now en aged by the switch wipers, is busy or not. f this trunk line is busy, the test contact 91 with which the private wiper 71 is in enga ement will ich ground potential will serve to maintain the line switching relay 63 short circuited and also to energize the relay 55. The rotar ma'gnet circuit is therefore again complete and the same cycle of operations is repeated whereby,the switch wipers advance into engage ment with the next set of contacts. It will be seen then, that the relay 55 will operate as an interrupter to step the switch wipers around through the medium of the-rotary contact-is reached and rotary magnet retracts its armature, the relay 55 cannot again energize and the switching relay 63 being no longer short circuited is energized in series with the relay 55. The relay 63 is of such high resistance, that relay 55-remains inoperative. By the attraction of its armaturethe switch ng relay (33 opens a contact l in the circuit of the release magnet 56 to provide against the denergization of relays 50 and 51; shifts the private wiper from connection to the up or terminal of relay 63 intoconnection wit 1 holding conductor 48; and disconnects the incoming line conductors from the windings of the line relay 50 and extends them instead by way of the line wipers 70 and 72, .and the'ron- ,ductors 93 and 95 to the line relay ot' asecond selector switch at the main exchange.

This second selector switch has not been shown but is understood to be similar to the selector E. The line and release relays of the second selector are now energized in the usual manner, whereby ground is placed upon the conductor 94 in order. to provide a holding circuit for the selector E and the line switch C. This holding circuit may be traced as follows: From ground on conductor 94, bank contact 91, wiper 71 and upper armature of relay 63 and its working con-- are controlled in the usual and well known manner to extend the connection to the desired subscriber. It should be mentioned here that a repeater is usually included in each trunk line to the main exchange, thereby ermitting the use of two-conductor trun in the well understood manner. lint since my invention is confined to the branch equipment nothing would be gained by showing in detail these trunks or the selectors to which theyextend.

Having briefly explained the ordinary operation of the selector E incident to the serving of-an unlimited service subscriber, I will now proceed to consider its operation when seized by a restricted service subscriber who desires to call the main exchange, and will explain how its operation in such case is modified by my invention. It will he eviw dent that inasmuch as the selector switch is required to operate differently, dependent upon the kind of line to be served, it must be able to discriminate in some way between .the automatic switches at the main exchange the different kinds of calling lines by which -it is seized. To this end the fourth conductor 47 is added to the trunk line and is grounded or not grounded at the individual line switch of the calling line, dependent upon whether the calling subscriber is to have his service restricted or not. In the case now under consideration, where it is assumed that the substation A is not to be given access to the main exchange, the terminals 38 and 39 associated with the individual line switch C will be soldered together.

To proceed, when the line of substation A is extended by the operation of the line switch C to the selector switch, the conductor 47 will be grounded b the engagement of bank spring 32 with the contact 36. The calling subscriber will now manipulate his calling device in accordance with the digit 0, desiring to obtain a main exchange connection, whereby the switch shaft is raised as before to'thetenth horizontal level of bank contacts, and is then automatically started rotating. The rotary movement does not cease when an idle trunk is reached, as in 'the former case, but continues independent of the busy or idle condition of the trunk lines. This insult is due to an alternative circuit for relay 55, closed when the switch shaft reached its uppermost position, and which may be traced as follows: ground at (F, terminals 38 and 39 (now soldered together), bank spring 32, contact 36, conductor 47, armature 75 and its re ting con tact, shaft controlled springs 57, contact springs 84, ofiuiormal springs 58, and the winding of relay 55 to battery 15. It will be seen then that the junction point 80 will be maintained grounded independent of the private wiper 71, whereby the selector will continue to rotate until the wipers pass the last set of contacts in the bank. On the eleventh rotary step the shaft cam 85 operates to switch the rotary off-normal springs with the following results: By the separation of contact springs 84 the previously described circuit including conductor 47 is broken, whereby the rotation is stopped; by the separation of contact springs 82 the energization of the switching relay 63 is prevented; and finally, through the medium of contact springs 86, 87, and 88, ground G is substituted for ground G in the circuit of the line relay 5(). Since the above circuit now includes the secondary of the transformer of the busy signaling machine, the calling subscriber will be given the busy signal, and will accordingly replace his receiver.

I will now refer to Fig. 2 in order to describe briefly a modification of my invention in which the same is applied to a so called selector connector switch. It has been thought unnecessary to show all the details of this switch, consequently everything except the bare operating circuits has been omitted. At this time reference is had to ll. S. Letters Patent #1,16i,-t79, granted Dec. 14, 1915 to Gerald Deakin. As previously mentioned a selector connector is of" utility inan automatic private branch exchange of a capacity of 90 lines or less, in which case the selectors such as the selector E would be omitted andselector connectors such as the one shown in Fig. 2 substituted therefor. The specific substitution mentioned would be accomplished by removing the selector E and connecting 'the conductors 100, 101, 102, and 103, respectively, of Fig. 2, to contacts 34, 35, 36, and 37, of Fig. 1.

A calling subscriber, whether restricted service or not, who desires to connect with another local subscriber, will remove his receiver, whereupon his line switch operates to extend his line to an idle selector connector, which is then controlled in a two digit operation to connect with the wanted line. Should a subscriber whose service is not restricted desire to call a main exchange subscriber, the first digit to be called will be the digit 0, whereby the vertical magnet VM is controlled by the line relay K to raise the switch shaft to the tenth level. The sluggish relay M is in series with the vertical magnet and is maintained energized during the series of impulses to close a cir cuit for the private magnet PM. When the shaft reaches its uppermost position the contact springs 133 and 1.31 are closed, thereby bringing about the energization of relay H, which operates to effect the switching of the rotary magnet RM from directive to automatic control. The shaft controlled springs 157, are also closed at this time, but without effect, for the calling line is not restricted as to its service and conductor 102 therefore will be nngrounded. When the relay M and the private magnet dei nergize at the end of the series of impulses the side switch wipers are advanced to their second position in the usual manner, whereupon a circuit is completed for the rotary magnet! in, series with the interrupter relay I, which magnet than operates to rotate the switch wipers under control of the private magnet in search of an idle trunk line.

From the foregoing the operation in case a restricted service subscribercalls the main exchange may be readily understood. When the switch shaft arrives at the tenth level and the contact springs 157 are closed, the grounded conductor 102 is extended to the private magnet PM, which accordingly is prevented from deenergizing at the end of the frst series of impulses, and the side switch wipers are thereby held in first 0- sition. The rotation of the switch is t us effectually prevented. At the same time the calling subscriber is given abusy signal by the connection of the busy signaling machine Q to the lower conductor of the trunk line.

. Having described my invention what I ,8 consider to be new and (ltSlP to have protected by Letters Patent will be pointed out in the ap )ended claims.

What claim as my invention is:

1. In a telephone system, anautmnatic selo-lector switch having directivcly controlled primary. movement for selecting groups of lines and automatic secondary move|nenthr select an idle line in a group. means for cans ing the primary movement oi said swit h and for initiating the secondary movement.

and means for continuing the scconda'y movement whether all thelines in the group. selected in the primary movement are busy or not.

an automatic switch, having means for testing saidlinesand for selecting an idle one, a Second automatic--s\vltcli having access to said first switch. means For operating said switches. and a cucuit controlled from said first switch and effective. to cause said sec-. ond switch to pass over said lines while testing whether the said lines are busy or not.

3. In a telephonesystem. a temporai'-il v 50 established connection including movable contacts in a first auton'iatic-switch and termina'ting in a second ,automatic switch, a

trunk line-means for operatingsaid second switch to connect with said trunk line when .5 the same is idle. and additional means'controlled from said first switch for ,causing said second switch to pass by said trunk line whether idle or not.

4. In a telephone system. a temporarily 40 established connection includipg movable contacts in a'first automatic switch and terminating in a second automatic switch. a group of trunk lines. means for operatlng the said second switch to select. an idle one.

' of said trunk lines. and means controlled 'from said first switch for causing said second switch to pass over allof said trunk lines whether idle or not. In a telephone-system.subscribers lines of different character. a selectocswitch. a'

group of trunk'lines. means for extending a calling line to said switch and for control ling the same to select an idle one of said trunk lines including automatic. means for 5 causing said selector to pass over busy trunk lines, and a circuit closed only when the calling line is of a particular kind torcausing said selector to pass over all of said trunk lines whether busy or not.

6. In a telephone system. a plurality of subscribers lines. a selector switch. a group oftrunk lines, means for ('nntrollil'lg said switch over a calling one of said lines to select an idle one of said trunk lines including means for causing said selector to' passover 2. In a telephone system. a group of lines.

busy trunk lines. and means for preventing certain of. said subscribers lines from having access to said trunk lilies. said means comprising a circuit closed only when one of the latter subscribers is calling and effective to cause said selector to pass over all of said trunk lines whether busy or not.

T. In a telephone system. subscribers lines of diti'erent"character, a selector switch, a

group of trunk lines, means for extending a scalling'linc to said switch and for controlling the same to select an idle one of said trunk lines including automatic means for causing said selector to pass over busy trunk lines, a circuit closed only when the c:'ll-ling.line is of a particular kind for caus- 'mg said selector to pass over all of said lrunk lines whether busy or not, aml meahs operated when all the said-trunk lines. are.

unsclcctable for transmitting a busy signal to the calling subscriber.

H. ln'a telephone system, a. plurality of subscribers lines. a selector switch. a group of trunk lines. means for controlling said 'sw-itch over a calling one of said lines'to select an idle one of said trunk lines including means for causing said selector to pass over busy trunk lines. means for preventing certain-oi said subscribers lines from having access to said. trunk lines, said. means comprising a circuit closed only when one of the latter subscribers is calling and effective to cause said selector to pass over all of said trunk lilies whether busy or not. and means operated when all the said trunk lines are unselectahle for transmitting a busy signal selector. to pass over all of the lines in the selected group whet-her busy or not, and means .for preventing the closure of said circuit when a particular one of said groups is selected. n i.

11). in a telephone system, subscribers lines of different character. a selector switch accessible to said lines, a plurality of groups of trunk lines.rneans for controlling said switch over a calling line to select a desired group ot trunk lines and an idle line 11'! the selected'group including means for causing said selector to pass over busy trunk' lines. a circuit efl'ective'to cause said selector to pass over all of the lines in the selected group whether busy or not, said circuit normally opcn at two points, means for closing said eircuitatone point only when the calling line is of a particular character, and means for closing said-circuit at the other point only when a particular group of trunk lines has been selected.

11. In a telephone'system, a trunk l1ne terminating in an automatic selector sw tch, other lines, means for operating sald switch to select an idle one of said other lines including automatic means for causing said switch to pass over busy lines, and additional automatic means, for causing sald switch to pass over all of said lines whether busy or not. v

12.In a telephone system,'a trunk line terminating in an automatic selector switch, other lines, means for operating said switch to select an ,idle one of said other lines including automatic means for causing sard switch to pass over busy lines, and additional means for causing said switch to pass over all of said lines whether busy or not, said last means comprising a circuit including a conductor of said trunk line.

13. In a telephone system, subscribers lines, a trunk line terminating in an autom'atic switch, an individual switch for each line responsive to a call thereover for connecting with said trunk line, means for operatingsaid first switch over a connected calling line, a circuit including a conductor of said trunk line effective when closed to limit the connecting possibilities of said first switch, said circuit normally open at two points, means in said first switch for closing said circuit at one point, and means in certain of said individual switches for closin said circuit at the other point.

matic switch, an individual switch for each subscri'bers line responsive to a call thereover to connect with said trunk line, means for operating said first switch over a con.-

nected calling line, a circuit including a con-' 'ductor of said trunk line, means in certain of said individual switches for grounding said conductor when the said trunk line is seized, and means responsive to such grounding to limit the effective operation of said first switch.

15. In a telephone system, subscribers lines, a trunk line having line and test conductors and terminating in an automatic switch, an individual switch for e'ach,sub-

scribers line responsive to a call thereover i n a telephone system, subscribers lines, a trunk line terminating in an autoa selector switch, another line, means for connecting a calling line with said trunk, means for controlling said switch over a. connected calling line to establish connection with said other line,and a circuit including a conductor of said trunk line closed onl when a calling line of a particular kind is connected thereto, said circuit effective to prevent said switch from connecting with said other line and for giving a busy signal to the calling subscriber.

17. In a telephone s stem, an automatic selector switch having irectively controlled primary movement for selecting groups of lines and an automatic secondary movement over the lines in a group to select an idle line in a group, means for causing the primary movement of said switch and for,

initiating the secondary movement, and means for continuing said secondary movement over all the lines in a group selected in aprimary movement whether all the said lines are bus or not.

18. In a telephone system, subscribers lines of different character, trunk lines, and an automatic switch'accessible to a calling one of said subscribers lines and controllable thereover to select an idle one of said trunk lines, including means for causing said switch to pass over the busy lines, and additional means for causing said switch to pass over either idle or busy lines, the operation of said last means depending pm the character of the calling subscribers mes.

19. In a telephone system, an automatic selector switch having a directively controlled primary movement for selecting groups of lines and an automatic secondary movement to select any idle line in a group, meansfor ,causing the primary movement of said switch and for initiating the secondary movement, and means for continuing the secondary movement whether all the lines .in the groupselectedin the primary movement are idle or not. 1

20. In a telephone system, an automatic selector switch having a. d rectively controlled primary movement for selecting groups of lines, and an automatic secondary movement to select any idle line in a group,

means for causing the primary movement of said switch and for initiating the secondary movement, and means for continuing the secondary movement over all the lines in a group selected in the primary movement whether all the said lines are idle or not.

21. In a telephone system, an automatic selector switch having a directivelv controlled primary movement for selecting groups of lines, and an automatic se'r-ondarv movement to select any idle line in the group. llll ans for causing the primarv mova- Tnuni. of said switch and for initiafina the se ondary movement; and means for on- "said switchfto select one of said 1 lines, means for initiatin an'automaticsec- V movement Of sa d switch to; S lect, .un i le'line in theselected group of lines, 25.

the 'secondaryr-movementof switch. w en o5lpart of theJine's' in the V e r "ground onftheiourth conductoi" nmk line fornventing saidswitchffnm 75 3 ends.

movementforselecting an idle line in a" 'hnes in a .moirement w ether all the said line'swb am of id' lines are idle. p

,22. In a. telephone-systezmfs trunk line terminating in an automatic switch, groups of lines accessible tofsaid switch, means for seizing sai'd trunk line andjfor'operiting said switch to select one of said gploups of lines, means for initlatin automatic seconda movement of'sai'd switch to, select any 1 le line in the selected 'group'of lines, f1 and means operative alt one-timefor'conthe secondary movement of- -said' switchiwhenall jthe lili s: in" t;1j;e selected";

tinumg an meansopemtiye atone time for continu all the lines selected group are'i :24. In -a) telephone system, an eutomatic";

selector switch-having a.*dqreotivelg con trolled movement for 9a ecting groups of lines and qnautomaticsecondary group, means for cau'si the pi'imary movelilies in the selected group,,are bu 40 ni,a, 0

ment of said switch an for initiati the 'movement of said whether all the o n 25. In a. telephone syste ur conduct-or trunk line term-mating 1n an auto.-

- matic switch, said switch having a directiv'ely controlled fimei'y'mouement :for S81- lectin" groups o lines and an'automati'c secon ary movement to select an idle line in a. group,-means for ceusingjthe primary;

4 matic switch mid switch having ,tively controlled ,primary movement to se- 'lect groups oflines'and 'an automatic sec- 23,. In a telephones'ystem, a, trunk me ter- [mating in en autoniaitic switch, "groups of lines accessible to said, switch,

seizing said trunk: line and vfoi opemting" tqr 'pmvent'in am tively iconticlled movement, and nieans' elm u'sive- 0 o O l n, of saihi l ines for continumg the secondary an ldlellne m agroup means for ca movement ofsaitl switch and for initiating I the secondary movement,- a.nd means. controlled over the fourth conductor of said. i

ductorgtrunk line, terminal/ting in an auto- 1 ondary movement to select an idle line in a 4 group, means'for causing the prime move-- ,mentnf saidswitchenjdv forinitiating the sov a l l gi x voverthe foiirthjccnduct'on of end: 1 e" g "switch fromlconnectin'g' mommy movement means ma'tic said' switch l1 l f 1 a? I ect' groups 0 I inesan ondsry movement to select" $1 3615 line up mam eriew i 9 m s- I 1 .ment' said-swltbli an tor mit gnjthe secon' fl'ymovement, means for plagc ingi connecting wi 1,; 28,.- In a telephone system, a. line terminating in {an autonl ti s z uiy 11 i m m s mwcvement m select groups pflineg V 'an automatic secondary movement to switch" having a directive omm ed, in

the primary movemento "said switch initlating thesecond movemen and means {86 for grounilingtne-conductor o said nun]? line for reventing said switch from conw; f w w. now-1s. 

